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47. Timber Mechanics. —Tests of green and air-dry material of mountain beech were completed during the year, but computation of values for the latter are incomplete. Five tree-green values show the timber in a slightly less favourable light than was indicated by one-tree values reported tentatively last year. However, there is no doubt that the timber will have a high use-value as a medium weight, close and even textured, white hard-wood, well above average (for its density class) in toughness. Values for air-dry material tested at 134-per-cent. moisture content, and uncorrected (as yet) to the standard 12-per-cent. figure, show that mountain beech is superior to the denser red beech in toughness (as indicated by work to maximum load in bending—--15-8 in. lb./cu.in), and extreme fibre stress in bending (14,460 lb./sq.in.). The density in the air-dry condition is 41 lb. ,/cu.ft. as compared with 44 lb. for red beech and 34 lb. for Southland silver beech. 48. Tests on the Denison toughness tester confirmed the unsuitability of some imported hickory and ash for use in handles ; indicated the limitations of rata and tanekaha for a similar purpose ; and failed to show any significant difference between sap-stained and non-sap-stained insignis pine. A series of tests in progress on tawa is concerned with the toughness/moisture content relationship at moisture contents ranging from green to air dry. 49. Timber Physics. —Work on wood anatomy may conveniently be considered under four headings : (a) The assembly, sectioning, examination, and description of material from species absent from or poorly represented in the Forest Service reference collections. Permanent slides added during 1949-50 totalled 180. Identification keys are constantly being revised for the major commercial woods. Photomicrographs taken during the year using excellent equipment loaned by the Wellington Technical College are to illustrate a comprehensive bulletin on the identification. of the indigenous timbers. A critical study of the indigenous-tree and small-tree species of the family Myrtacese was completed during the year by a member of the staff as an honours degree thesis. (b) Identification by macroscopic features or microscopic examination of commercial timbers from local and overseas sources. The identity and properties of many timbers, whose importation for special purposes has been proposed, are requested in many inquiries received from importers and from Government Departments ; during the year inquiries concerned timbers from all over the world. Samples requiring microscopic identification exceeded fifty during the current year. (c) Identification of fragmentary, partially decomposed, or fossilized woody material to assist botanical and geological studies. Inquiries of this type have increased considerably ; Police Department inquiries were among those handled during the year. (d) Studies correlating structure with other physical properties or indicating fibre characteristics as an index to use. Variation in mountain-beech timber is being studied from the microstructure angle. 50. Studies of physical properties of indigenous and exotic timbers again comprised an important part of timber-research work. One intensive study relating to Corsican pine planted in 1907 in Whakarewarewa forest and sampled in 1949 showed a range of density of 29 to 37 lb. a cubic foot (at 12-per-cent. moisture content). 51. The experiments in chemical poisoning of larch and Corsican pine, designed to retain the ease of barking characteristic of spring and early summer by killing the trees at that time, were completed by felling and examination of the balance of the treated trees. The treatment had been ring-barking and the application of sodium arsenite in flour paste in the spring of 1948. The interim results reported last year were that larch

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